The proposed investigation seeks new information about the effects of cocaine on brain activity in relation to behavior. An experimental approach using electrophysiological recording, stimulation, and behavioral methods will be applied to study the central nervous system effects of cocaine. Cats prepared with indwelling cortical and subcortical electrodes will serve as subjects. We are especially interested in investigating possible actions of cocaine in modifying excitability of components of the limbic system and related structures. The effects of small doses of the drug in altering thresholds for detection of focal stimulation of various subcortical sites will be determined. Changes in spontaneous electrophysiological activity and responses to brain stimuli will be studied in subjects trained to respond to direct subcortical stimulation. A second objective will be to determine the effects of long-term daily administration of cocaine on the above measures. A third series of studies will examine effects of cocaine on stimulation induced changes in brain activity (evoked potentials, recruiting responses, and post-tetanic potentiation). This series of experiments is designed to provide basic information related to the pathophysiology of cocaine use. More generally, the investigation may also contribute new information about the role of temporal lobe structures during states of vigilance and excitement as well as during the behavioral aberrations and perceptual distortions which may be induced by psychotropic drugs.